纯跟踪算法 python

纯跟踪算法（pure pursuit algorithm）是一种用于自主车辆导航的算法，它是基于车辆与路径之间的距离来计算车辆下一步要采取的行动。该算法基于假设，即路径是由一系列连续的线段组成的，并且车辆在每个时间步长内只能前进一段距离。在每个时间步长内，纯跟踪算法会计算车辆与路径之间的最短距离，并将车辆的目标点设置为路径上与车辆最近的点。然后，算法会计算车辆应该前进的距离和方向，并将这些信息作为控制器的输出。

以下是使用Python实现纯跟踪算法的示例代码：

import math

class PurePursuit:
    def __init__(self, lookahead_distance):
        self.lookahead_distance = lookahead_distance

    def get_target_point(self, path, current_pos):
        min_distance = float("inf")
        target_point = None
        for i in range(len(path)-1):
            p1 = path[i]
            p2 = path[i+1]
            distance = self.distance_to_line(p1, p2, current_pos)
            if distance < min_distance:
                min_distance = distance
                target_point = self.get_closest_point_on_line(p1, p2, current_pos)
        if target_point is None:
            target_point = path[-1]
        return target_point

    def calculate_steering(self, current_pos, current_heading, target_point):
        dx = target_point[0] - current_pos
        dy = target_point - current_pos
        alpha = math.atan2(dy, dx) - current_heading
        return alpha

    def distance_to_line(self, p1, p2, p3):
        return abs((p2-p1)*p3 - (p2-p1)*p3 + p2*p1 - p2*p1) / math.sqrt((p2-p1)**2 + (p2-p1)**2)

    def get_closest_point_on_line(self, p1, p2, p3):
        dx = p2 - p1
        dy = p2 - p1
        u = ((p3-p1)*dx + (p3-p1)*dy) / (dx*dx + dy*dy)
        x = p1 + u*dx
        y = p1 + u*dy
        return x, y

    def get_control(self, path, current_pos, current_heading):
        target_point = self.get_target_point(path, current_pos)
        alpha = self.calculate_steering(current_pos, current_heading, target_point)
        distance = math.sqrt((target_point-current_pos[0])**2 + (target_point-current_pos)**2)
        speed = distance / self.lookahead_distance
        return speed, alpha